Use an enum for ES|QL format parameter

Author: pquentin

output/schema/schema.json

@@ -35,7 +35,7 @@ export interface Request extends RequestBase {
     /**
      * A short version of the Accept header, e.g. json, yaml.
      */
-    format?: string
+    format?: EsqlFormat
     /**
      * The character to use between values within a CSV row. Only valid for the CSV format.
      */
@@ -87,3 +87,14 @@ export interface Request extends RequestBase {
     tables?: Dictionary<string, Dictionary<string, TableValuesContainer>>
   }
 }
+
+export enum EsqlFormat {
+  csv,
+  json,
+  tsv,
+  txt,
+  yaml,
+  cbor,
+  smile,
+  arrow
+}